The present invention relates in general to fuel filters which incorporate a water separation and collection feature in combination with a heater. More specifically the present invention relates to fuel filters which include a variety of features which are intended to provide a design which is convenient to use and to service and which is cost effective to manufacture.
Diesel fuel tends to contain a relatively high level of impurities such as particulate matter and water as compared to the corresponding levels in other liquid hydrocarbon fuels. As a consequence, diesel fuel typically needs to be filtered before injecting the diesel fuel into the engine. The concern over the levels of particulate matter and water in the diesel fuel are significant due to the problems which can be caused. Particulate matter can clog fuel lines and fuel injectors and cause deposits to be formed in the combustion chamber. When water-laden diesel fuel is run through a fuel system and engine, the presence of water can cause the fuel injection system to malfunction due to rust, corrosion, deposits, etc. Excessive levels of water may lead to catastrophic injector nozzle failure due to the effects of steam expansion and/or lubricity effects.
In cold weather, diesel fuel becomes more viscous and, as a result, flows through the fuel system more slowly. Due to the presence of water in the diesel fuel, there is a higher probability of fuel line freeze. Even if the fuel does not freeze in the fuel line, the higher viscosity, due to the fuel gelling, will cause the fuel filter to restrict the flow therethrough. The problems of the fuel gelling and increased viscosity are complicated by having an increased amount of water in the fuel. If there is insufficient fuel reaching the combustion chamber, the engine will be starved and, as a result, will not run or will not run efficiently.
In order to address the issue of water-laden fuel and fuel viscosity in cold weather, fuel filters have been designed with water separation and collection arrangements and with heaters. In one arrangement, the water and other contaminants in the diesel fuel are collected on the outer surface of the filter medium and from there, drop to the bottom portion of the housing and are collected in a suitable collection bowl. In another arrangement, a centrifugal flow path is used to separate the higher density fluid (i.e., water and particulate matter) from the lower density fuel.
With regard to the addition of a heater, heater devices used in combination with diesel fuel filters have become accepted due to the successful results which have been achieved. Initially, the heaters were adapted to preexisting fuel filters, but now it has become common to incorporate the heater as an integral, although modular, part of the fuel filter package. The use of a heater achieves an efficient degree of heat transfer with the fuel.
While the enhancements of water separation and the addition of a heater are significant, a number of other considerations are introduced by these two enhancements. For example, what path should the fuel follow for proper heating of the fuel? What style of thermostat should be used and where should it be installed in order to control the temperature? What style of housing is preferred and what is the easiest way to install and replace the filter element? These are only some of the questions which need to be answered when designing a fuel filter with the water separation capability and with a heater. The specific style of heater is also a consideration as is the method of draining the collection bowl. Some of these considerations have been the subject of issued patents and the following listing is believed to be a representative sampling of these earlier design efforts:
______________________________________ PATENT NO. PATENTEE ISSUE DATE ______________________________________ 3,473,666 Humbert, Jr. Oct. 21, 1969 4,298,465 Druffel Nov. 3, 1981 4,321,136 Matsui Mar. 23, 1982 4,406,785 Siefer Sep. 27, 1983 4,437,986 Hutchins et al. Mar. 20, 1984 4,477,345 Szlaga, Jr. Oct. 16, 1984 4,502,955 Schaupp Mar. 5, 1985 4,580,542 Kawabata Apr. 8, 1986 4,997,555 Church, et al. Mar. 5, 1991 5,244,571 Church, et al. Sep. 14, 1993 4,387,691 Marcoux, et al. Jun. 14, 1983 4,596,224 Prager Jun. 24, 1986 4,608,161 Niemeier Aug. 26, 1986 ______________________________________
Even with all of the design variations and features which have heretofore been invented, there are other improvements and enhancements which have not, prior to the present invention, either been offered as part of a fuel filter or combined with a number of other features and enhancements into one cooperating assembly. Improvements in the housing design, the drain valve, the lid and filter cartridge relationship, and the water-in-fuel sensor are all incorporated into the present invention in a novel and unobvious manner. Further, a novel and unobvious heater ring is incorporated as part of the fuel filter according to the present invention and this provides benefits as to heating of the fuel and separation of the water from the fuel. The overall result from the present invention is an improvement in the service method, an improvement in the compact design, and an improvement in the cost effectiveness of the fuel filter design.